Aims: The purpose of the present proposal is to obtain funds necessary to preserve the scientific integrity of our on-going double blinded multi-center clinical trial and to honor our moral and ethical commitment to the patients participating in the present study. The original study design anticipated enrollment of eighty patients between 1/1/83 and 7/1/83. Unfortunately, actual enrollment was not completed until 7/20/84. The initial study promised all patients access to intrathecal (IT) human fibroblast interferon (IFN-B) after they had been on the study for two years. Early enrollees expect to be treated with IFN-B in the spring of 1985. As the study will not be completed before 7/20/86, we must be prepared to offer treatment to the original controls (who received placebo) in a manner which preserves the blinding of the study until it is finished. Methodology: After completion of two years on the present clinical trial, individual patients will be offered additional treatment. They will not be informed as to the prior therapy which they received. Patients who were original controls will be "crossed over" to receive IT-IFN-B for 24 weeks, according to the protocol schedule. Patients who were original recipients will be given false LPs. Data regarding exacerbations and clinical status of patients will continue to be transmitted to the statistics center by the examining physician. Serial laboratory tests to be performed include: NMR, CT, VER, CSF (IgG, MBP, oligoclonal bands, IFN levels) and serum IFN levels. Long Term Objectives: If the efficacy of IT-IFN-B in reducing exacerbations is confirmed, then this method of treatment could be used on a widespread basis in the treatment of MS patients to prevent major disability via reduction or elimination of exacerbations.